Question: What has been the sister city of Tver since July 6th, 1997?
Paraphrase: Since July 6,1997, what is Tver's sister city?
SPARQL (Wikidata): SELECT ?obj WHERE { wd:Q2288 p:P190 ?s . ?s ps:P190 ?obj . ?s pq:P580 ?x filter(contains(YEAR(?x),'1997')) }